Blasting cap



Patented May a, wee I v restate an @FFEQE CHARLES E. LICKLE, OF"WILMINGTON, DELAWARE, ASSIGNOR T HERCULES POWD COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION 03 DEJLAW 112,}; g

BLASTENG CAP Application filed December 29, 1930. Serial No. 505,333.

My invention relates to improvement in blasting caps and more articularly to the provision of means where y accidental firing of a cap through contact of the lead wires 5 with a sourceof current will be positively avoided.

' It is well known that blasting caps comprise a container or casing in which an explosive charge, as for example, fulminate of 1c mercury, is contained. Extending into the casing a pair of lead wires, the ends of which within the casing are connected by means of a bridge wire embedded in the explosive charge or in a more readily fire initiating charge. The lead wires in their extension from the cap, and ordinarily they extend some four or five feet, are mainly insulated, but their end portions are left bare 'of insulation in order that they may be con- 2 nected into a firing circuit.

It has been well recognized that the uninsulated end portions of the lead .wires afiord an opportunity for accidental discharge of the cap, since in carrying caps to their point of use, for example, in a mine, the lead wires I caps through inadvertent contact of the bare ends of the lead wires with a circuit or source of stray current. It has, for example, been suggested to twist the bare ends of the lead wires together for a distance in order to shortcircuit them and various devlces have been provided for connecting the bare ends of the lead wires or securing them in contact with circuit.

The various means heretofore suggested for the avoidance of inadvertent firing of caps have not proven satisfactory forvarious reasons. wires are twisted together for a distance, it is necessary in order for the twist to be reasonabl effective that it be extended to the insulate portions of the wire and desirably even beyond. The twisted ends are disadone another with a view to elfecting a shortterial bent mto angular form and provided Where the bare ends of the lead vantageous, since before the cap can be used the ends must be untwistecl and the untwisted ends being deformed and kinked are in an undesirable condition for making an eficient connection with a. firing circuit. 4

The various devices for connecting the lead wires or for holding the lead wires in contact with one another. have been found unsatisfac- 'tory, since 1n all cases they are extremely dificult to remove, the ends of the wires usually being deformed in their removal and they do not afford any greater degree of protectlon, if as great, as that afi'ordedby the twisting of the bare wires.

Now in accordance with my invention, ll prov de means whereby inadvertent firing of lastm caps is prevented, which means may be rea ily applied and, i at the same time when the cap 1s to be used, maybe removed readily and without appreciable distortion of the uninsulated end portions of the lead wires.

In accordance with my invention I provide means whereby the uninsulated end portions of the lead wires may be shor t-circuited, -the means or shunt bein of such a character as to be readily applie to the wires and to be positioned to maintain itself thereon and,"

at the same time, to be readily positioned for removal without appreciable distortion of the wires. Preferably, the means or shunt will be of such a character as to on application automatically position itself to grip and retain itself in engagement with the wires.

The means or shunt in accordance with my invention may be made of any desired conducting material and may be resilient or nonresilient, as may be desired. Thus, the means or shunt may be made of brass, steel, etc. The means or shunt will desirably comprise a relativelynarrow strip of conducting madesirabl bear against the ends of the insula tion at t e juncture of the insulated and uninsulated portions of the wires. If the means or shunt be of resilientmaterial, it will be maintained in position and in contact with the end portions of the lead wires by its own resiliency, which will cause the arms to separate and throw the apertures out of alignment when released. On the other hand, if the means or shunt be'non-resilient material and properly positioned, the two arms will be spread to throw the apertures out of alignment and cause the shunt to grip the wires to maintain itself thereon.

It will be appreciated that an advantage of my short-circuiting device is that the harder the attempt to pull it from the lead wires the tighter it grips said lead wires, unless it is intentionally released by bringing the two ends of the clip together. This advantage of automatic increase of gripping power is in no way evident in previous devices, and comprises one of their defects.

Having now indicated, in a general way, the nature and purpose of my invention, I will proceed to a detailed description of a preferred embodiment thereof with reference to the accompanying drawings in which:

Figure 1 is a view of a blasting cap with 'lead wires embodying my invention.

Figure 2 is a perspective View of means i or shunt embodying my invention.

In the drawings a indicates a blasting cap of any usual or desired construction, extending from which are a pair of lead wires 6, b insulated throughout the major portion of their length and having uninsulated end portions 6', b to enable connection of the cap into a firing circuit. The cap a may, for ex- I ample, comprise a casing within which is positioned a detonating'charge or detonatin g charges upon which an initiating charge is superimposed, the detonating charge or initiating charge being adapted to be fired electrically through the medium of .the usual bridge wire connected across the lead wires and embedded in the detonating charge or initiating charge within the casing.

0 indicates a short-circuiting means or shunt in accordance with my invention. The shunt a, as shown, is formed of a relatively narrow strip of conducting material bent into angular form to provide the two arms d, d, adjacent the ends of which are formed the apertures e,

e As shown in Figure 1, the shunt is applied to the uninsulated end portions b, b of the lead wires by drawing the arms d,cZ together, brin ing the apertures e, e into alignment and passing the end portions of the lead wires I throughtheaperturese,e. The position of the arms on application to the end portions of the leadwires is shownby dotted lines in Figure 1. When the shunt is in position the arms cl, d

.are separated, in the case of non-resilient material, or separate due to the resillence of the material, causing the apertures e, e to go out of alignment and consequently causlng the lead wires to be tightly gripped by the where the shunt is made of non-resilient ma-.

terial the arms will be positively spread apart when the shunt is desirably positioned.

As will be obvious, the shunt may be readily removed from the lead wires by merely bringing the arms d, d together and slipping the shunt ofi the free ends of the wi res, which may be readily accomplished since when the arms are together the apertures e, e will be in alignment and no resistance to the withdrawal of the wires through the apertures will be oifered. Further, as will be obvious, the shunt in retaining itself upon the wires through spread of the arms and consequent non-alignment of-the apertures e, 6 will not cause any material distortion of the wires and hence when the shunt is removed the wires will be in perfect condition for connection into afiring circuit.

It will be noted that when the arms of the shunt are separated causing the lead wires to be gripped at their points of passage throiwh the apertures e, e, the shunt will not only e firmly secured to the lead wires, but since the shunt engages uninsulated portions of the and also through contact with one another will be assured.

It will be noted that desirably when the shunt is in final position, that is with the arms (1, d separated, the arm adjacent to the insulated portions of the wires will engage the uninsulated portion adjacent to the termination of the-insulation.

What I claim and desire to ters Patent is:

1. In combination with an electric blasting cap provided with lead wires having uninsulated end portions, a conductive shunt member bent upon itself and having apertures adjacent its free ends through which the end portions of the lead wires pass, the shunt member being maintained on the lead wires through non-registration. of the said apertures.

2. In combination with an electricblasting cap provided with lead wires having uninsulated end portions, a conductive shunt member formed of resilient material and bent upon itself and having apertures adjacent its free ends through which the end portions of the lead wires pass, the said member being maintained on the lead wires by its resiliency.

3. In combination with an electric blasting cap provided with lead wires having uninsulated end portions, a. conductive shunt member formed by bending upon itself astrip protect by Lethaving apertures adjacent its free ends, the

unmsulated end portions of the lead wires extendin through said apertures and the member eing retained on the lead wires by separation of its free ends.

4. In combination with an electric blasting- 

